The pro-EU centrist Emmanuel Macron has vowed to unite a divided and fractured France after winning a decisive victory over the far-right Front National candidate Marine Le Pen in the country’s presidential election.

Macron, 39, a former economy minister who ran as a “neither left nor right” independent promising to shake up the French political system, took 66% to Le Pen’s 34%.

His victory was hailed by his supporters as holding back a tide of populism after the Brexit vote and Donald Trump’s victory in the US election.

Addressing thousands of supporters in the grand courtyard of the Louvre, the vast Paris palace-turned-museum, Macron said he would defend France and Europe. He said Europe and the world are “watching us” and “waiting for us to defend the spirit of the Enlightenment, threatened in so many places”.

He promised to unite a divided and fractured France, saying: “I will do everything to make sure you never have reason again to vote for extremes.”

Speaking of his meteoric rise and victory that was not forecast even a year ago, he said: “Everyone said it was impossible. But they didn’t know France!”

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Who is the new French president, Emmanuel Macron? – video

Despite the wide margin of the final result, Le Pen’s score nonetheless marked a historic high for the French far right. Even after a lacklustre campaign that ended with a calamitous performance in the final TV debate, she was projected to have taken almost 11m votes, double that of her father, Jean-Marie Le Pen, when he reached the presidential run-off in 2002. The anti-immigration, anti-EU Front National’s supporters asserted that the party had a central place as an opposition force in France.

Turnout was the lowest in more than 40 years. Almost one-third of voters chose neither Macron nor Le Pen, with 12 million abstaining and 4.2 million spoiling ballot papers.

Macron, who has never held elected office and was unknown until three years ago, is France’s youngest president. Next Sunday, he will take over a country under a state of emergency, still facing a major terrorism threat and struggling with a stagnant economy after decades of mass unemployment. France is divided after an election campaign in which anti-establishment anger saw the traditional left and right ruling parties ejected from the race in the first round for the first time since the period after the second world war.

François Bayrou, an ex-minister and Macron’s centrist ally, said: “He is the youngest head of state on the planet [which] sends an incredible message of hope. Macron is giving hope to people who had no hope. Hope that maybe we can do something, go beyond the [left-right] divide that no longer makes sense.”

Le Pen swiftly conceded defeat. She said she had won a “historic and massive” score that made her leader of “the biggest opposition force” in France and vowed to radically overhaul her Front National party. Her promise to “transform” the far-right movement left open the possibility that the party could be expanded and renamed in an attempt to boost its electoral chances. It was a major step in the political normalisation of her movement.

The outgoing Socialist president, François Hollande, who was once Macron’s mentor and had appointed him economy minister, said: “His large victory confirms that a very great majority of our citizens wanted to unite around the values of the Republic and show their attachment to the European Union and show France is open to the world.”

On Monday Hollande embraced his successor as the two men attended a ceremony at Paris’s Arc de Triomphe to commemorate victory over the Nazis in the second world war. Hollande walked beside Macron to the Tomb of the Unknown Soldier at the monument, where they laid a wreath.

Macron and Hollande attend a ceremony at the Arc de Triomphe in Paris on Monday. Photograph: Philippe Wojazer/Reuters

Macron’s victory came not only because voters supported his policy platform for free market, pro-business reform, and his promises to energise the EU, coupled with a leftwing approach to social issues. Some of his voters came from other parties across the political spectrum and turned out not in complete support of his programme but to stop the Front National.

In a political landscape with a strong hard left and far right, Macron faces the challenge of trying to win a parliamentary majority for his fledgling political movement En Marche! (On the Move!) in legislative elections next month. Without a majority, he will not be able to carry out his manifesto promises.

After the Brexit vote and the election of Trump as US president, the race for the Élyséewas the latest election to shake up establishment politics by kicking out the figures that stood for the status quo, ejecting the mainstream parties that have dominated French politics for 50 years and leaving the political novice Macron to do battle with the far right.

His victory comes after a bitter campaign with Le Pen in which she accused him of being part of an elite that did not understand ordinary people and he said Le Pen represented the “party of hatred” that wanted a “civil war” in France. The runoff pitted France’s most Europhile candidate against its most Europhobe.

In Brussels and Berlin, there was relief that Le Pen’s anti-EU, anti-globalisation programme was defeated.

A spokesman for the German chancellor, Angela Merkel, said it was a “victory for a strong and united Europe” while the European commission president, Jean-Claude Juncker, said French voters had chosen a “European future”.

The office of the British prime minister, Theresa May, said she “warmly congratulates” Macron on his victory and “we look forward to working with the new president on a wide range of shared priorities”.

Trump, who will meet Macron on 25 May at the Nato summit in Brussels, tweeted: “Congratulations to Emmanuel Macron on his big win today as the next president of France. I look very much forward to working with him!” Earlier in the campaign, he had declared Le Pen the strongest candidate.

In a congratulatory statement, the Kremlin, which was widely seen as backing Le Pen, urged Macron to overcome mutual distrust and join forces to ensure international stability and security.

Hours before the end of campaigning on Friday night, Macron’s campaign was hacked, which Paris prosecutors are investigating. Hundreds of thousands of emails and documents were dumped online and spread by WikiLeaks in what his campaign called an attempt at “democratic destabilisation”.

Macron, a former investment banker and senior civil servant who grew up in a bourgeois family in Amiens, served as deputy chief of staff to Hollande but was not part of the Socialist party.

What is in Macron's in-tray as president?

France’s youngest president takes over a country exhausted by years of unemployment and facing a constant terrorist threat. So what will his first moves be? First, Macron, who comes from no established political party, needs to appoint a prime minister and a cabinet, and win a parliamentary majority in next month’s election.

Next, he will need to swiftly fulfil some of his manifesto promises: including streamlining France’s strict labour laws in favour of businesses, overhauling the ethics rules for politicians, and strengthening ties with Germany's Angela Merkel and the rest of the EU.

In 2014, Hollande appointed him economy minister but he left government in 2016, complaining that pro-business reforms were not going far enough. A year ago he formed En Marche!, promising to shake up France’s “vacuous” and discredited political class.

His troubled five-year term left France still struggling with a sluggish economy and a mood of disillusionment with the political class. The country is more divided than ever before. More than 230 people have been killed in terrorist attacks in little more than two years, the political class is questioning Islam’s place in French society and more than three million people are unemployed.

The rightwing candidate, François Fillon, once seen as favourite, was badly damaged by a judicial investigation into a string of corruption allegations, including that he paid his wife and children generous salaries from public funds for fake parliamentary assistant jobs.

The Guardian view on the French election: Good luck, Mr Macron. You will need it | Editorial

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The ruling Socialist party, under its candidate Benoît Hamon, saw its score plunge to 6%, while the hard-left Jean-Luc Mélenchon finished fourth.

The final round marks a redrawing of the political landscape, away from the old left-right divide towards a contest between a liberal, pro-globalisation stance and “close the borders” nationalism. Le Pen has styled the election as being between her party’s “patriots” and the “globalists” whom she says Macron represents.

Voters in France went to the polls on Sunday in the first round of the presidential election. The top two candidates, independent Emmanuel Macron and far-right Marine Le Pen, go into a run-off in a fortnight. Find out where each drew most support and what happens nextFrench presidential election 2017 – first round live updates